Feature: add "requested destination" or other save specs?

[tlambert03]

Should we add something like requested_destination to MDASequence?

I don't (immediately) want to add a whole lot of specific saving stuff, but a single field requesting a destination path might be very useful for possible downstream writers: It would provide a directory, base name, and extension. Writers could then increment that base name as desired (until any further spec added instructions on that sort of thing)

@ianhi ?

[ianhi]

Sounds good to me! Maybe also an extra metadata dictionary to allow for downstream uses we can't conceive of now?

Are you imagining these all as required arguments, or optional?

[tlambert03]

everything optional. you should probably always be able to call MDAEvent() or MDASequence() without args.

[ianhi]

ooh right because requested_destination is the name. Rather than something like "save_params" which would be it's own object

[tlambert03]

yeah, for now, the writer (over in pymmcore-plus) would have all the parameters. This is just a bare-minimum sort of start.
I can imagine something like this:

seq = MDASequence(requested_destination='...')

class MDARunner():
    def run(self, events: MDASequence):
        if seq.requested_destination:
            for writer in self.writers:  # these are the objects with as-of-yet undetermined parameters
                writer.set_destination(seq.requested_destination)

but... I dunno

[ianhi]

for writer in self.writers:

a little bit of an aside here: in a couple places you've given examples of how to work with many writers. Is that just a generality thing, or are their use cases im not thinking of for multiple writers? unless we think of something like the napari display as also being a writer

[tlambert03]

yeah, good question. I can't see an immediate use case for multiple writers... but I do think that so far, the writer "spec" fits a general category of something that I can see multiple of: namely, anything that wants to be notified at the start, end, and each frame of an acquisition, let's call it a handler:

class Handler:
    def sequenceStarted(): ...
    def frameReady(): ...
    def sequenceFinished(): ...

so, I'm kinda mentally leaving that possibility open :)